Make sure we do not write bogus reflog entries.

The file format dictates that entries are LF terminated so
the message cannot have one in it.  Chomp the message to make
sure it only has a single line if necessary, while removing the
leading whitespace.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-update-ref.c

@@ -23,8 +23,6 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 			msg = argv[++i];
 			if (!*msg)
 				die("Refusing to perform update with empty message.");
-			if (strchr(msg, '\n'))
-				die("Refusing to perform update with \\n in message.");
 			continue;
 		}
 		if (!strcmp("-d", argv[i])) {

refs.c

@@ -925,6 +925,7 @@ static int log_ref_write(struct ref_lock *lock,
 {
 	int logfd, written, oflags = O_APPEND | O_WRONLY;
 	unsigned maxlen, len;
+	int msglen;
 	char *logrec;
 	const char *committer;
 
@@ -958,24 +959,30 @@ static int log_ref_write(struct ref_lock *lock,
 				     lock->log_file, strerror(errno));
 	}
 
-	committer = git_committer_info(-1);
+	msglen = 0;
 	if (msg) {
-		maxlen = strlen(committer) + strlen(msg) + 2*40 + 5;
-		logrec = xmalloc(maxlen);
-		len = snprintf(logrec, maxlen, "%s %s %s\t%s\n",
-			sha1_to_hex(lock->old_sha1),
-			sha1_to_hex(sha1),
-			committer,
-			msg);
-	}
-	else {
-		maxlen = strlen(committer) + 2*40 + 4;
-		logrec = xmalloc(maxlen);
-		len = snprintf(logrec, maxlen, "%s %s %s\n",
-			sha1_to_hex(lock->old_sha1),
-			sha1_to_hex(sha1),
-			committer);
+		/* clean up the message and make sure it is a single line */
+		for ( ; *msg; msg++)
+			if (!isspace(*msg))
+				break;
+		if (*msg) {
+			const char *ep = strchr(msg, '\n');
+			if (ep)
+				msglen = ep - msg;
+			else
+				msglen = strlen(msg);
+		}
 	}
+
+	committer = git_committer_info(-1);
+	maxlen = strlen(committer) + msglen + 100;
+	logrec = xmalloc(maxlen);
+	len = sprintf(logrec, "%s %s %s\n",
+		      sha1_to_hex(lock->old_sha1),
+		      sha1_to_hex(sha1),
+		      committer);
+	if (msglen)
+		len += sprintf(logrec + len - 1, "\t%.*s\n", msglen, msg) - 1;
 	written = len <= maxlen ? write_in_full(logfd, logrec, len) : -1;
 	free(logrec);
 	close(logfd);